Various classes of adhesives are used in binding techniques utilized in the bookbinding industry. For example, synthetic emulsion adhesives, such as polyvinyl alcohol or ethylene vinyl acetate emulsion polymers, are used on endpapers, for tipping, for gluing-off operations, for lining, casing-in, spine gluing and side gluing, and on special stencil applicator case makers. Hot melt adhesives consist of polymers, tackifier resins and waxes. Hot melts are used mainly as one-shot adhesives for pocket-books and magazines, in multi-shot applications in the production of catalogues, and in burst binding. Starches derived from maize, potato and tapioca are used for producing pastes, generally for the hand-binding section of the trade. However, some are used in operations such as endpapering and tipping, also hand case making in leather. Starches can be modified into dextrins, which increases their solid content and their tack and speed.
Case making is one of the more demanding bookbinding techniques with respect to the adhesive properties required of the bookbinding adhesive utilized therein. Animal glues are mainly used for case making and lining, and only occasionally in unsewn binding lines. Animal glues consist of one or more kinds of gelatine in a solution of water. They give aggressive tack with a medium-set speed. Such glues are available in slab jelly form, or as harder granules. Since animal glues are derived from natural materials, they are much subject to seasonal factors and tend to vary with their source of supply. Operators using them have to be skilled in achieving the right degree of dilution and tack. Most animal glues age and become brittle under dry, warm conditions, as is normally evident from the condition of the spine of a book kept for some time in a centrally heated home. In addition, as a natural product, animal glues are susceptible to enzymatic and bacterial attack.
It would be desirable to provide a synthetic adhesive composition which exhibits the set speed, tack and adhesion of animal glues in case making applications, yet has the advantages over animal glues of improved product consistency, less odor, increased compostability and resistance to enzymatic and bacterial attack.